A061469 GCD of the amicable pairs: a(n) = gcd(A002025(n), A002046(n)).

4, 2, 4, 4, 8, 8, 105, 16, 92, 16, 135, 819, 10, 45, 585, 16, 8, 10, 16, 16, 8, 44, 4, 4, 14, 8, 16, 98, 16, 585, 8, 8, 8, 8, 8, 4, 8, 105, 16, 8, 135, 8, 10, 50, 10, 5733, 8, 585, 10, 855, 16, 10, 4, 10, 10, 585, 32, 10, 8, 16, 14, 8, 16, 4, 8, 310, 8, 16, 8, 10, 50, 855, 14, 8, 10

Offset: 1

Author

Jason Earls, Jun 11 2001

Keywords

• nonn

Comments

The pairs are ordered by the smaller number. - David Wasserman, Jun 18 2002

Examples

			a(1) = gcd(220, 284) = 4;
a(2) = gcd(1184, 1210) = 2.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from T. D. Noe)
• Eric Weisstein's World of Mathematics, Amicable Pair.

Crossrefs

Cf. A002025, A002046, A259180 (amicable pairs).

Programs

Mathematica

With[{s = PositionIndex@ Array[DivisorSigma[1, #] &, 10^6]}, Flatten@ Map[GCD @@ # &, Apply[Join, Map[Function[n, Select[Subsets[Lookup[s, n], {2}], Total@ # == n &]], Sort@ Select[Keys@ s, Length@ Lookup[s, #] > 1 &]]]]] (* Michael De Vlieger, Oct 22 2017 *)

Extensions

More terms from David Wasserman, Jun 18 2002

a(22) corrected by T. D. Noe, Aug 15 2010